This invention relates to a thyristor with a gate and a plurality of emitter shunts distributed over the cathode surface and to the use of such a thyristor.
It is already known from J. Burtscher, E. Spenke "Kurzschlussemitter und Thyristorzundung" Siemens Forschungsund Entwicklungsberichte 3, pages 234-47 (1974) to suppress unwanted turn-on of a thyristor--particularly when a voltage age rise (du/dt) is applied--by means of more or less regularly distributed short-circuits (shunts) between n.sup.+ emitter and p-base. In addition, it is known to dispose this emitter shunt in the vicinity of the gate (turn-on electrode) to give it a special shape or to arrange it suitably in order to control the development of the turn-on front, as disclosed in Swiss Patent Specification No. 578,254 or to facilitate the propagation of the turn-on front as described in Swiss Patent Specification No. 572,279 or in the report by T. C. New, D. E. Cooper, "Turn-on characteristics of beam fired thyristors", IEEE Record IAS Conf. 8.-11.10.73, Milwaukee/Mich., pages 259-265. In this case, the emitter shunting serves the purpose of diverting a displacement current produced homogeneously over the whole thyristor area by the voltage rise (du/dt). If the emitter shunting is distributed substantially homogeneously over the cathode surface, a precisely defined proportion of this displacement current reaches each shunt in the interior of the cathode surface. Addition components of displacement current are lost at the emitter shunting at the cathode edges, however. Thus at the cathode edge at the gate side, for example, apart from the homogeneous displacement current, an additional displacement current produced under the gate also appears. As a result of this inhomogeneous distribution of the whole displacement current over the cross-sectional area of the thyristor, the voltage-rise (du/dt) resistance of the whole component is low. At the cathode edge the turn-on threshold is actually reached much earlier than in the interior of the cathode surface because of the localized increased displacement current there.